Mrs May said: "Unlike a coalition of chaos and instability led by Jeremy Corbyn, a Conservative government led by me will get on with the job of making life in the United Kingdom even better.

"That means we are prepared to face up to the big long-term challenges facing this country.

"The internet has brought a wealth of opportunity, but also significant new risks which have evolved faster than society's response to them.

"We want social media companies to do more to help redress the balance and will take action to make sure they do.

"These measures will help make Britain the best place in the world to start and run a digital business, and the safest place in the world for people to be online."Under the plans, social media firms will have to take action to stop search terms directing users to inappropriate sites.

It is hoped the move will stop children accidentally stumbling on porn, with some adult channels featuring X-rated videos that have titles which play on the names of well-known films and characters.

The measure would also include hate speech and other sites that could be harmful to youngsters.

Age restrictions on apps to stop young children accessing damaging content will also be expanded.

Responding to Mrs May's announcement, Liberal Democrat former Cabinet minister Alistair Carmichael said: "It is certainly bold of the Conservatives to boast how they can protect people on the internet the day after the NHS has been hacked with a loophole apparently built by the US Government.

"Government and technology companies must do more to find a real solution to problematic content online but having a government agency deciding what constitutes acceptable free speech isn't it.

"We need to be working with technology companies to address the problem of hate speech, not pretending it's an easy problem that can be solved with a press release."